18-Agent Marketplace Simulation Tests What Keeps Self-Interested LLM Agents Cooperating

arXiv·medium signal

Left unconstrained, self-interested agents drift toward defection in repeated social dilemmas, collapsing gains from trade. Using a marketplace of 18 LLM agents (DeepSeek-V3) with complementary needs, the study identifies which formal mechanisms layered on unrestricted communication are sufficient to maintain market stability and how resilient they are to adversarial attack. Concrete evidence for designers of multi-agent economies and negotiation systems.